CHAPTER 4. CONCLUSIONS AND
MANAGEMENT IMPLICATIONS
Vegetation was reduced by a minimum of 40
percent and more often was completely eliminated
as a result of ATV traffic at the test sites. Soils were
compacted (except sands and gravels), displaced,
or loosened, making it available for transport
(erosion) by water. Of the soils tested, the hydraulic
conductivity (soil’s ability to absorb rainfall) was
reduced by more than one-half, while the interrillerosion coefficient (soil erosion) increased by more
than one-half as a result of ATV traffic. Results
from the high-intensity rainfall-simulation test
concluded that freshly disturbed soils on an ATV
trail produce, on average, 10 times more sediment
than undisturbed soils.
At the study’s outset we asked three defining
questions: Are natural resources being affected by
The dust study (conducted only at the LBL site)
ATV traffic on forested lands; if so, by how much;
was designed to measure the soil displaced by
and does the way an ATV is equipped make a
aerial erosion caused by ATV traffic. The goal was
difference?
to understand the relationship among soil types,
vehicle traffic, and dust creation. A secondary
In short, this study concludes that ATV traffic can
objective was to evaluate the effects dust had on
adversely affect natural resources and the way the
native human health and vegetation.
vehicle is equipped does not make a statistically
significant difference. The study further concludes
The results of the study (see appendix C) concluded
that—of the vehicles tested—all ATVs contribute to
that ATVs can cause significant amounts of soil
the effects regardless of type and equipment.
migration by aerial displacement. Dust particles
were captured 200 feet from the trail. Spikes
The effects are considered adverse when the
in average-particulate loads greater than 150
natural resources (vegetation, soil, water, and air)
micrograms per cubic meter were common as
have been reduced or changed in a manner that
vehicles passed the active monitors positioned 3
prevents them from maintaining and performing
to 6 feet off the trail. ATV traffic was relatively light
their ecological functions. The ramifications of the
during the experiment. When the numbers of riders
effects are manifested in the removal or destruction
are substantially higher, air concentrations would be
of vegetation, including forest-floor litter, the
expected to be well into the unhealthful range where
exposure and destruction of plant-root networks,
the forested edges of the trails inhibit air circulation.
the exposure of bare soil, soil erosion, and dust
Where trails are open with adequate air circulation,
migration as a result of bare-soil exposure.
the particulate loads have lower impacts on human
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health. The passive samplers deployed at head-
Straight runs showed the least amount of soil
height confirm a substantial atmospheric loading
displacement. The difference in soil displacement
that could affect the riders’ respiratory systems.
for an uphill or downhill section was five to eight
times greater than on level-straight sections.
The evaluation of dust effects on vegetation
Therefore, trail managers should make monitoring
suggests that ATVs cause only minor perturbations
and maintaining curves and turns a high priority,
(disturbances). Some stomatal (pore) blockage
followed by uphill and downhill sections of trail.
was observed, as were surface accumulations of
Curves require extra attention to ensure that they
dust that may periodically inhibit photosynthesis
are designed and constructed for proper armoring
and respiration, but little superficial damage to
and drainage.
the cuticle was evident in the images captured by
a scanning electronic microscope. Because of
The data also imply that straight sections of trail
frequent rainfall at the test site, it is unlikely that
will require less maintenance, especially if these
the effects are long lasting or a cause for serious
sections are located away from weaker soils. This
concern (Padgett 2006).
is an important distinction to manage as forests
involve and work with volunteer groups to make
There are two surprising results from the study.
their contributions meaningful and effective.
First, sport-model vehicles (lighter weight ATVs)
cause as much disturbance as the heavier
Perhaps the most important management
utility-model vehicles. There were no significant
implication of this study is that ATV traffic should
differences between the level of disturbance caused
be limited to trails. The data gathered in this study
by sport- or utility-model vehicles. The heavier,
overwhelmingly support this direction. Areas that
more powerful utility vehicles reached the targeted
continue to allow cross-country travel can only
disturbance levels in fewer passes than the sport
expect to see a further reduction in the ability of
two-wheel-drive models; but, when the number of
natural resources to maintain their composition and
passes was the same, the levels of disturbance
structure and perform their natural functions. Other
were the same for each vehicle type.
studies related to soil and vegetation disturbance
indicated that the rehabilitation of these areas will
Second, there were no distinguishable differences
take many years, especially those in arid climate
between the level of disturbance caused by a
zones (Cole 1986). Some may never recover
vehicle with standard manufacturer-issued tires or a
without assistance.
vehicle equipped with more aggressive after-market
tires. Ultimately, all tire and vehicle combinations
The study also suggests that limiting ATV traffic to
tested caused the same levels of disturbance.
trails is not enough to protect the natural resources.
Trail planning and design, particularly the trail’s
Four trail features were tested: a curve, downhill,
location, are key considerations for limiting natural-
uphill, and straight runs. For all soil types, curves
resource disturbances. The primary objective of a
were most susceptible to soil displacement, followed
well-designed ATV trail is to protect and conserve
by uphill and downhill runs regardless of soil type.
the natural resources while providing an enjoyable
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and challenging experience. The experience is
parameters based on scientific principles (i.e.,
the purpose of the trip! The design phase should
the rainfall rate at which soils begin to experience
identify destinations as well as areas to avoid, such
runoff, and the magnitude of rainfall events). The
as soils that are easily disturbed, wet areas (riparian
Kisatchie National Forest sets a rainfall limit of 2
zones), ridge tops, and sensitive wildlife habitats
inches before closing its ATV trails, and they remain
and archeological sites.
closed until the soil regains its absorption capacity.
Similar parameters have been developed for other
Trail alignments should be curvilinear with short
forests.
sight distances. Avoid tight turns and steep climbs,
as these trail features are susceptible to high levels
Information that describes the effects of dust
of soil disturbance and erosion. Use contours and
migration as a result of ATV traffic could also prove
the vertical alignment to facilitate drainage across
to be an effective tool for monitoring trail use and
and away from the trail. Avoid constructing trails
keeping natural resources in balance. Managers
on the fall line. Use water diversions as often as
could use such information to establish seasonal
necessary to move water off the trail and onto the
closures, employ dust abatement techniques, and
forest floor. These practices will significantly reduce
design better trails to reduce soil migration.
erosion and sedimentation.
Casual observations made during the study also
The data also suggest setting limits or developing
suggest a need to develop sustainable riding
natural-resource tolerance levels as a way to
practices to assist riders to improve their riding
manage and reduce the effects of ATV traffic on
habits and information to enhance their knowledge
the natural resources. Consider for example the
about the affects of ATV traffic on natural
hydraulic conductivity, interrill coefficient, and dust-
resources. Riding practices would include: slower
migration data. The hydraulic conductivity of soil
speeds through curves, avoiding wheel spins and
(soil’s ability to absorb rainfall) is a way of estimating
fish tailing, and avoiding travel through wet areas.
soil saturation and when overland flow begins. This
Information should also be provided about why it is
information is very useful for establishing natural-
important to avoid these sensitive areas.
resource tolerances and developing trail-closure
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